Switch for telephone systems



March 17,1931. s vm ET AL 1,796,402

SWITCH FOR TELEPHONE SYSTEMS fi I m Original Filed Oct. 18, 1926 2Sheets-$heet l 46 34 v I I1wfimr- John Eamn-HczbEfT EJMEEHE Dgcf March17, 1931. J;ASAVIN AL 1,796,402

SWITCH FOR TELEPHONE SYSTEMS Original Filed Oct. 18, 1 926 2Sheets-Sheet 2 Jul-m. Eamn-HmbEfEdmard Emgd Patented Mar. 17, 1931 JOKNSAVIN AND BOBEBT EDWARD BOYD,

or. LIVERPOOL, ENGLAND, assrenoss, m:

KESNE ASSIGNMENTS, TO ASSOCIATED TELEPHONE & TELEGRAPH COMPANY, OF

KANSAS CITY, MISSOURI SWITCH FOR TELEPHONE SYSTEMS lpplioatlonflledoctober 18, was, Serial No. 142,224,

June 12,

The present invention relates-to improveinents in or relating toswitches 92/ used in automatic telephone systems and bile moreparticularlythe invention is co cerned with improvements in a particularty of switch, it should be understood that the V rious features of theinvention where applicable can apply to other types of switch than thatmentioned. In British Patent No. 17 9,157 a type of switch is describedand illustrated in which the wipers move in a continuously forwardsdirection in a single plane under the control of a stepping magnet. Aswitch of similar type but somewhat different construction is describedin British Patent No. 131,716. Usually such switches are providedindividual to each -subscribers l-ine and are adapted to operateautomatically to select an idle first selector switch when a subscriberlifts his receiver. When utilized in such positions the switches are notused very extensively even on the busiestlines, the motion taking placeonly at the commencement of a call, particularly if the wipers rest onthe contacts last used, if the wipers return to normal the switch makeshalf a revolution for every call. This switch howeveris also capable of,and is often used in other cases where it may be in almost continuousrotation; for instance where it is. used for controlling thetransmission of impulses in a register sender, or in anoperators impulsesender. In'such cases in order to avoid excessive replacement it isnecessary to a design the switch specially, and the object of thepresent invention isto improve switches of this character so that theywill have a much longer life than hitherto.

The principal features of the invention consist in the special design ofthe wipers, provision of a readily replaceable wiper-unit including aratchet wheel, specialhardened steel shoes also replaceable atpoints ofexcessive wear, a special constructionof pawl from single steel pressingwith a hexagonal back stop and the utilization of a specially selectedmaterial for the parts found to wear most excessively.-

The invention will be better understood by referrin to the accompanyingdrawings and description of one form of carrying the invenand in GreatBritain November 5, 1925. Renewed 1930.

tion into efl'ect which relates more particular ly to a switch havingthe eneral features of ritish Patent No.

construction described in 17 9,157 previously referred to.

L In the drawings Fig. 1 shows a side view of the switch and Fig. 2shows a front view. Figs. 3 and 4 show in perspective view the ratchetwheel on which it is fitted and the wiper assembly unit. Figs. 5 and 6show the plan and elevation of the wiper shaft. Fig. 7 shows a crosssection of the wiper assembly illustrating clearly the shape of thewipers and the arrangement of assembling them on the unit. Figs. 8 and 9"show the construction of the new pawl in plan and elevation.

Referring to Fig. 7 of the drawings it will be noted that the wipers arespecially shaped; the object of this shape is to increase the resiliencyof the wipers and-for that purpose the arms 10 connecting the centralpart of the wiper 11 to the parts 12 which actually engage with contacts13 as shown in Fig. 1 are of longer length than the radial distancebetween the central part 11 and the parts 12. In prior constructionspart 10 was usually equal to the radial distance between the centre ofthe part 12 and the outside of the central part 11.- These wipers-areformed from the parts 12 is clearly seen from Fig. 4, the

wipers being mounted in pairs and meeting so as to form a V at theirpoints of contact as shown for all the wiper pairs, except the pair atthe extreme right is slightly difi'erent, the shoes of this pair ofwipers meeting on a plane as is also clearly shown in Fig. 4.

These wipersare assembled in a single unit as shown in Fig. 4. This unitcomprises a metal tube 14 having a fixed hexagonal head 15 (Fig. 2) atone end and threaded at the other end. Fitting over the tube 14 is atub; '16 of insulating materia1,such as phenol fibre; then there aresuccessively fitted over the tube 16 an insulating washer 17 also ofphenol fibre which abuts a ainst the hexagonal head 15, a wiper 18 ig.2) a metal washer 19, anda second wiper 20; the wipers 18 and 20 areidentical in construction, the only difference being that the" partwhich engages, the contacts is deflected in opposite directions. in thetwo wipers so that they meet in the form of a V as shown in Figs. 4 and2. Abutting against the wiper 20 is amet al washer 21, after-this comesa piece of insulation 22 which is only shown in Fig. 4. This piece ofinsulation is exactly the same shape as the wipers, except that it isnot deflected at the ends and serves to prevent neighboring wiperscoming into contact in case of vibration being set up when the wiperscome on and off their contacts. It might be mentioned that in Fig. 4 sixpairs of wipers are shown, while in Fig. 2 only four pairs of wipers areshown. This simply illustrates. that the -number of wipers can be variedat will as will be readily appreciated from the construction of thewiper assembly provided that sufficient space is left on the wiper shaftand on the tubes 14 and 16. v

The insulation piece is then followed by another wiper, anothermetalwasher, the complemen-tary wiper of, the previous one .so as toform a pairand so on as before right up to the last wiper and afterwhich there is another head 15 of the tube 14; The ratchet wheel-and thewiper assembly thereby forming another insulating washer 23, Fig. 2, anda number disc 24. This is followed by a metal washer 25 and the wholebeing secured in position by a nut 26 threaded on to the end of, thetube 14.

It might be mentioned that the number disc consists of a stamping havinga cylindrical edge graduated as shown in Fig. 2, the graduation servingto show the particular contacts in the bankwhich the wipers areengaging. In order to ensure that the wipers will not rotate relativelyto one another, holes are punched in the head 15 of the tube 14, so asto cause the metal to projectso that. when the nut 26 is tightened u theprojecting points penetrate the phenol bre washer 17, and thecompression thereupon exerted if the nut is properly tightened upeffectively prevents the relative rotation of the wipers. This unitwhich is shown in Fig. 4 forms a complete wiper assembly'unit which canbe'readilyreplaced. The wipers are constructed of a nickel silver alloyof a temper sufliciently hard to cause a minimum amount of wear on thebank contacts, the bank contacts being also constructed of nickel silveralloy, but harder temper is used so that, as the wipersare more easilyreplaceable than the banks, it is ensured that the replaceable elementwill be the one which will be first worn. The ratchet wheel 27 is shownin Fig. 3, and has welded into it a tube 28 at the far end. The tube 28g is of adiameter-such that it will just fit'into thehole of thetube14wA disc of henol fibre 29 separates the ratchet wheel 2 from thereplaceable unit. The" unit is supported on ashaft- 31 of a diameterwhich just fits inside the tube 28, so that the wiper unit with theratchet wheel can rotate freely about the shaft. The shaft passesthrough the holes in each side of, the frame 32; this frame is'astamping having connecting bridges 33 and 34 and two parallel sidepieces to which the reference 32 is fixed in Fig. 2 of the'drawing'. Theshaft is held in position by a link 35 having a slot adapted to engagewith the grooves 37 of the shaft 31. These grooves are shown moreclearly in Figs. 5 and 6. This link turns about a screw .38 which actsas a pivot and serves to secure the link in position. It will be atonceapparent from the construction that by turning the link the shaftcan; be removed from the hearings in the, frame 32 and when the whole ofthe wiper assembly including the ratchet wheel can bejremoved while thewiper assembly and the ratchet wheel can be detached separately so thateither part .or

both parts can be replaced as desired. The wiperco'ntact springs, thatis the springs which connect the. circuits to the. central parts of therotating wipers are indicated in Fig. 2 i

by the reference 39.} This is not very clear, but it will be sufiicientto indicate that they come between the wipers 18 and 20 respectively andare fixed in the contact bankin the same way as the bank contacts butina. special position. "Like the bank contacts they consist of stampingsand having. their ends curled in opposite directions so as to engage thecentral part of each wiper; These contact springs are also constructedof nickel silver;

33 and 34, oneside of the contact bank is adjustable by means of thenut40 and screw 41. The electrofiiagnet 42 is supported on the bridge piece34 and is provided with a U shaped yoke 45, which has extensions 46through a hole in which a shaft 47 similar in general design. to thewiper shaft 31-pass'es so that it can be secured in position and removedat will by operating a link member 47 ,which is similar to the link 35.This shaft in addition to sliding through the holes in the extensions46' passes through extensions 48 of the armature '49. It will thus beappreciated that the armature can be removed as readily as the wiperassembly. The arm 50 which forms an extension of the armature 49 isfitted at its in detail in Fi 8 and 9. From these figures it will be nothat the pawl 51 is formed of a single stamping which is U shaped; inplan but is curved in elevation following the curvature of the ratchetwheel, the part for engaging the ratchet Wheel is suitably shaped asshown at 52 and forms an extension of the bridge of the two limbs of theU.

It will be noted that the two limbs of theU pass on each side of theextension 50 and rotate about a pivot secured therein. A spring 53serves to normally press the pawl towards the ratchet teeth. It will benoted that by this construction a central planein Fig. 9 passes equallythrough the part 50 and the centre of the ratchet wheel, while the limbsare directly parallel to this line, so that it may be said that thearmature and pawl are in a direct line of action. This incontradistinction to constructions where the ratchet wheel or theextension piece of the armature is a much more satisfactory constructionand operates much more efli ciently giving a longer life and morereliable action. The part 52 is hardened to reduce wear. On theextension of the armature and integral therewith is a projection 54carrying a har'denedsteel shoe 55 for engaging with the steel spring 56which effects the return motion of the armature and pawl andincidentally, as in this construction of switch the wipers advance' onthe release of the electromagnet, steps the wipers. A considerableamount of wear is liable to take place at the junction between the parts55 and 56 and for this purpose part 55 is made detachable so that it canbe readily replaced. The'second projection is also provided on the .part50 on which is fitted a bush 57 of insulating material,

' phenol fibre, ebonite or, the like, which engages with the interrupterspring 58 to open the magnet circuit by separating the spring 58 fromthe spring 59 and thereby interrupt ing the circultof the electromagnetto permit it to de-energize. The lever 60 is provided with a cam shapedhead 61 for the pur pose of adjusting the stroke of the pawl andarmature. It should be mentioned that the pawl 51 is provided at thefendwhich engages with the ratchet wheel-but on-the opposite side with aface 62 which is adapted-to rest normally against a hexagon headed nut63 so that the engaging surfaces are sufiicientlyextensive to ensurethat no considerable wear will take place at this point. Springs 54, 56are constructed of steel, while the ratchet wheel is made of hard Tobinbronze capable of withstanding hard and constant wear. It will be notedthat the pawl as designed in addition to being strong and reliable isalso light in weight. The action of the ratchet wheel 27 the pawl 51-andthe detent'spring 64, is desi ed to give positive and accurateregistration of the wipers as they step along the bank contactsandtooperate together with as i little absorption of energy as possible,the major portion of the energy of the restoring spring 56 then beingavailable for overcoming the inertia of the wipers and the stepping ofone contact to the next- Although.

spring is formed of hard nickel sliver and simply consists of a plainstamping with a t rounding oil of the end which engages slig the teeth,so as to leave an approximately square end for enterng between theteeth, and a rounded off end to prevent any rubbing friction aganst theradial sides of the teeth, as will be obvous to those versed in the art.

By describing briefly the operation of the device note will be inade ofthe particular points on which stress is laid in the present inventionwith a vlew to overcoming the wear of the various parts. When theelectromag net is excited it attracts the armature 49 which thereuponturns about the armature shaft. and forces back spring 56 by thev shoe55 and forces the pawl 51 forwards,-so that the part 52 can engage thenext tooth, the

spring 54 ensuring this, while the projection 57 forces the spring 58from engagement with the spring 59. It will be noted that of the partsmentioned the armature shaft, the shoe 55, and the sprin 54 are allreadily replaceable, while no di culty would be encountered in replacingany of the springs 56, 57 and 58, which are secured in position bysuitable screws and insulations in a manner well known in the art. Againthe ratchet wheel is readily replaceable. When the electromagnetde-energizes, whether due to the springs 58 or 59 openm or due to someother part of the magnet circuit being open, the spring 56 forces backthe armature and the pawl 51 which thereupon causes the ratchet wheeland the wipers thereon to advance one step, the wipers are liable towear as they rub over contacts 18 and thereforeare constructed in aseparate replaceable unit. The detent spring 60 in the position to whichit is set. Bearing t:

in mind that this operation takes place in any thing up to 80 times persecond, when .the

switch is in operation, and that the switch may be re uired to make over1,000,000 ste s in a perio of six to twelve months, it will satisfactorymanner as in the present case.

Also it would be appreciated that as materials have been speciallyselected by numbers of experiments the present invention-is designed togive a much longer life to the switch before any replacement whatever isnecessary than iihat we claim as new and desire to se-' cure by LettersPatent is 1. A wiper assembly for use in automatic telephone switcheshaving rotatable wipers comprising a tube on which the wipers are fittedas a separate and d1st1nctun1t,a second I tube fitting inside said firsttube to which. a

ratchet wheel is secured, said second tube and ratchet wheel beingdetachably secured to the wiper unit so as to make another larger unitwhich is readily removed and replaced in the switch.

2. A wi-per assembly as claimed in claim 1 in which a non-rotatablereadily removable shaft is provided as a support permitting the wipersto rotate freely, the shaft being .sup-

ported in fixed bearings and secured in position by a link deviceengaging a slot or slots near one end.

3. A switch for use in automatic telephone systems having rotatablewipers in which the pawl for operating the ratchet wheel is eonstructedfrom a single piece of sheet metal bent in the shape of a U withone-edge of the base of the hardened and suitably shaped to engage withthe teeth .of the ratchet wheel, and forming a continuation of a radialline extending from the center of the ratchet wheel. I

4. In an automatic switch for use in telephone systems, a set of bankcontacts argranged concentric-to a hub, a set of wipers integrallyformed on said hub and adapted to rotate over said bank contacts, saidwipers having arms arranged 1n a plane parallel to said bank contactsand extending from each side of said hub towards said bank contacts in adirection tangentto said hub, and a portion of each arm engaging saidcontacts bent at an angle from said arm but in the same plane andarranged in a radial line with each other and said hub.

5. In an automatic switch for telephone systems, a set of bank contacts,a set of wipers concentric to said contacts and adapted torotate overthem, an enlarged circular central portion-of said Wipers mounted on ahub, and a pair of arms on each wiper extending from each side of saidcircular portion in a direction tangentther'eto, the ends of said armsbeing bent to conform to the shape of said contacts I and the wholeforming in length than the radial distance said contact making portionand the center an approximate shaped structure.

' 6. In an automatic switch for telephone systems, a set of bankcontacts, a set of wipers arranged concentric to sa d bank contacts andin the same plane thereof, a circular central portion on said wipers,two arms extendlng tangentically from said circular portion towards saidcontacts, contact making portions on the ends of said arms bent at anangle but in the same plane therefrom to conform to the shape of saidcontacts, said arms beingbgreater etween of said circular portion of thewipers.

7. In an automatic switch for telephone systems, a set of bank contacts,a set of wiper-s adapted to rotate over said contacts in a forwarddirection, a circular central" portion of said wipers mounted on aninsulated axis,

wiper arms on said circular portion extending on opposite sides and inopposite. directi ons and tangent thereto, contact making portions onthe ends of said arms bent at an angle therefrom to conform to the sha eof said bank contacts and in a plane paral el thereto,

the length ofsaid wiper arms being greater than the radial distance fromthe bank consystems, a set of bank contacts, a set of wipers havingaccess to said contacts, a motor magnet having an armature adapted tooperate a pawl and ratchet wheel to rotate said wipers over. said bankcontacts, said pawl comprismg a s ngle U-shaped sheet of metal havingthe two open ends pivoted to the end of said armature and one edge bfthe base of the U flattened out and lying in a plane parallel to theradius of the ratchet wheel to engage with the teeth of said ratchetwheel;

9. In an automatic switch for telephone systems having rotatable wipersin which the pawl foroperating the ratchetwheel comprises a U-shapedmember in which an extension of the base of the U forms a pawl, andinwhich the free ends of the member extend separately from thepawl tothe point at which they are pivoted. I

' 10. In a pawl and ratchet mechanism a U- shaped member having a pawlformed at the lib base of the U-to engage with 'the teeth of the ratchetwheel and pivot points on saidmember comprising extensions of the areforming

